The Second Doctor used a hypercube to ask the Time Lords to return the soldiers kidnapped by the War Lords to their own time periods, as he could not do so on his own. The Doctor constructed this one from six separate white cards and merged them with his mind. Calling upon his people for help proved to be a personal sacrifice for the Doctor; it led to his exile on Earth, a forced regeneration into the Third Doctor, and the separation from his companions Jamie McCrimmon and Zoe Heriot. (TV: The War Games)